The present invention relates to a process for the recovery of TNT and aluminum from tritonal-containing military shells. The process uses a solvent in which the TNT is substantially soluble, but not aluminum. This results in a liquid solvent phase and a solid aluminum particle phase. The aluminum particles are recovered by conventional solid-liquid separation techniques, such as filtering, gravity settling, and the like. The TNT is recovered from the solvent by flashing or evaporating the solvent and recrystallizing the TNT.
Surplus munitions present a problem to the US military. Current budget constraints force the US military to prioritize its spending while effectively defending the interests of the United States. Defense budgets are further tightened because aging and surplus munitions must be guarded and stored. The US military regularly destroys a significant amount of its surplus munitions each year in order to meet its fiscal challenge. It also destroys a significant amount of munitions each year due to deterioration or obsolescence.
In the past, munitions stocks have been disposed of by open burn/open detonation (OBOD) methodsxe2x80x94the most inexpensive and technologically simple disposal methods available. Although such methods can effectively destroy munitions, they fail to meet the challenge of minimizing waste by-products in a cost effective manner. Furthermore, such methods of disposal are undesirable from an environmental point of view because they contribute to the pollution of the environment. For example, OBOD technology produces relatively high levels of
NOx, acidic gases, particulates, and metal waste. Incomplete combustion products can also leach into the soil and contaminate ground water from the burning pits used for open burn methods. The surrounding soil and ground water must often be remediated after OBOD to meet environmental guidelines. Conventional incineration methods can also be used to destroy munitions, but they require a relatively large amount of fuel. They also produce a significant amount of gaseous effluent that must be treated to remove undesirable components before it can be released into the atmosphere. Thus, OBOD and incineration methods for disposing of munitions have become impractical owing to increasingly stringent federal and state environmental protection regulations. Further, today""s ever stricter environmental regulations require that new munition and weapon system designs incorporate demilitarization processing issues. Increasingly stringent EPA regulations will not allow the use of OBOD or excessive incineration techniques, consequently, new technologies must be developed to meet the new guidelines.
Recovery and reuse methods, such as that of the present invention, are the most attractive alternative to the conventional destructive methods discussed above and can be used to recover substantially all of the munition components with very little waste generation. This state-of-the-art technology is feasible, safe, and relatively inexpensive. It also has the potential of meeting the recovery and reuse goals of demilitarization. Future demilitarization operations will be dominated by chemical conversion and recovery technologies that recover or convert the explosives and other components used in munitions manufacture to materials that can be recycled, or resold, in a cost effective environmentally acceptable manner.
One type of explosive system that presents a demilitarization problem are military shells that contain tritonal (a mixture comprised of TNT and aluminum powder) as the energetic component. Such shells also typically contain an organic liner material, such as an asphalt material, and a resin sealer. Clay is often dispersed within the resin matrix. The most common method used to remove tritonal from a shell is the use of a steam wand to melt the tritonal from the shell. Another method is to use autoclaves that are large enough to heat the entire shell, thereby melting the energetic material, which will then flow out of an open shell casing. Such methods have the disadvantage of melting not only the tritonal, but also the asphalt liner and resin sealer, resulting in a mixture of all these components. The use of steam also adds water that results in so called xe2x80x9cpink waterxe2x80x9d, that must also be treated before it can be released into the environment. Thus, the aluminum particles will mix with the TNT, asphalt liner material, and resin sealer. Such a technique results in a significant problem because the TNT, aluminum, asphalt, and resin are difficult to separate and purify once they are mixed together. Consequently, a significant amount of the aluminum powder that is dispersed in the resin and asphalt is unrecoverable.
In some instances, water condensate from the steam wand can react exothermally with the aluminum powder to produce an undesirable amount of heat. This undesirable amount of heat has the potential of causing the energetic material to spontaneously explode. Further, the asphalt liner has been shown to accelerate the TNT aging process, thus leading to unstable products that could initiate a spontaneous exothermic decomposition of the energetic materials. Water is also a contaminant in TNT and because it is difficult to separate it from TNT, the commercial value of the recovered TNT is reduced. A blend of such components also prevents its reuse as an explosive or its value in chemical conversion processes.
Therefore, there is a need in the art for a process that is capable of efficiently removing tritonal from a tritonal-containing military shell and recovering its individual components.
In accordance with the present invention there is provided a process for separately recovering TNT and aluminum particles from an explosive comprised of TNT and aluminum particles, which process comprises;
a) treating the explosive with a solvent in which TNT is substantially soluble and in which said aluminum particles are substantially insoluble, thereby resulting in a slurry of aluminum particles in TNT/solvent solution;
b) separating said aluminum particles from said TNT/solvent solution; and
c) recovering the TNT from the solvent.
Also in accordance with the present invention there is provided a process for removing an explosive comprised of TNT and aluminum particles from a military shell and recovering the TNT and aluminum components, which military shell also contains at least one organic liner component, which process comprises;
a) opening said military shell to expose the explosive and organic liner component;
b) treating the exposed explosive and organic liner components with a solvent in which TNT is substantially soluble, but in which said aluminum particles and organic liner material are substantially insoluble;
c) removing said explosive component from said shell and leaving the organic liner material, thereby resulting in a slurry of aluminum particles in TNT/solvent solution;
d) separating the aluminum particles from the TNT/solvent solution;
e) recovering said TNT component from said solvent.
In a preferred embodiment of the present invention the solvent is selected from the group consisting of acetone and cyclohexanone.
In another preferred embodiment of the present invention there is an additional steps of removing the organic liner material from the shell and rinsing the shell to an effective cleanliness so that the shell can be recycled as scrap material.
In yet another preferred embodiment of the present invention the separation technique for separating the aluminum particles from the TNT/solvent solution is selected from the group consisting of gravity settling and filtration.
In still another preferred embodiment of the present invention the TNT is recovered from the solvent by evaporating the solvent and recrystallizing the TNT.
In yet another preferred embodiment of the present invention the recovered aluminum particles are dried using a substantially inert gas, preferably nitrogen.
In another preferred embodiment of the present invention the solvent, after TNT separation, is condensed and recycled.
In still another preferred embodiment of the present invention the organic liner material, which remains in the shell after tritonal removal, is removed from the shell casing using a suitable second solvent, which is then flashed off, thereby leaving an organic liner concentrate.